Fatty acid composition of peanut seed oil in four varieties cultivated in Tunisia showed that linoleic (C18:2), oleic (C18:1) and palmitic (C16) acids account for more than 84% for Chounfakhi and Massriya and for more than 85% of the total fatty acids of Trabilsia and Sinya seed oil respectively. Seed oil contents were significantly different (P ≤ 0.05) and did not exceed 48%. The study of total phenolics revealed that Chounfakhi contained more total phenolics (2.1 mg GAE/g DW), followed by the Massriya and Sinya cultivars (1.35 mg GAE/g DW for each); Trabilsia presented the lowest total phenolic content with 1 mg GAE/g DW. Considerable antiradical ability was found, especially in the Trabilsia peanut seed cultivar (IC50 = 1550 μg/ml), the Massriya and Sinya cultivars had, respectively, 720 and 820 mg/ml IC50. In the Massriya variety the sterol fraction showed antibacterial activity against Listeria ivanovii, Listeria inocua, Pseudomonas aeruginosa, Staphylococus aureus, Enterococcus hirae and Bacillus cereus.